1. Field of the Invention
The present invention relates to an original document feeder to be equipped in an image forming apparatus such as a copying machine, and, in particular to such original document feeder for feeding original document stacked for example on a stacker tray to a predetermined process unit, and further guiding said original documents, after processing, to an original receiver.
2. Related Background Art
In the conventional original document feeder for use in a copying apparatus, a user cannot use the feeder until a preceding user completes processing of the original documents. In fact the users have to wait in line until the preceding user completes the processing. However such situation is naturally inefficient and wasteful in time.
For this reason there has been proposed an automatic original document feeder allowing, even during the processing of a set of documents, to set another set of documents, thereby capable of processing the new set of documents in succession when the processing for the preceding set of documents is completed.
For example the U.S. Pat. No. 4,248,529 discloses an automatic document handling apparatus comprising plural original document trays capable of stacking plural documents, a document feed roller for feeding the documents from the document tray one by one, copying means for copying the original document fed by said original document feed roller, control means for controlling the feeding of the original documents from the trays in such a manner that the document feeding from a reserved tray is started after a last document is fed from a tray, and a document receiving tray for receiving the thus copied original documents.
Also the Japanese Patent Laid-open No. 121136/1979 discloses a copying apparatus equipped with a mechanism for automatically feeding original documents to an exposure position, which comprises generating an electrical signal indicating a change in the copying conditions, when all the original documents constituting a predetermined set have been fed from a document stacking tray and the original documents of another set are to be fed.
The above-explained conventional apparatus functions in the following manner. An original document from a document stacking tray is supplied, from an end of a platen glass and along a path formed above said platen glass, to the other end thereof The document is then inverted by a guide member provided at said other end, and is guided to a predetermined position on the platen glass by a conveyor belt, from said other end. After the exposure, the document is discharged by the conveyor belt to the first-mentioned side of the platen glass.
However, such structure is associated with a drawback of requiring a long time for guiding the document to the predetermined position on the platen glass, regardless of the size of the original document